The product "A" in the above reaction is:

The reactant is a $$\mathrm{\beta\text{-}Keto\ Ester}$$, specifically $$\mathrm{Ethyl\ Acetoacetate}$$, containing both a ketone and an ester group.

When treated with ethylene glycol in presence of acid $$\mathrm{(H^+)}$$, the reaction forms a cyclic ketal.

Ketones are more reactive toward nucleophilic addition than esters because the ester carbonyl is resonance stabilised by the adjacent oxygen atom.

Hence, the reaction occurs selectively at the ketone carbonyl group.

Ethylene glycol condenses with the ketone group, eliminating water and forming a five-membered cyclic ketal $$\mathrm{(1,3\text{-}Dioxolane)}$$ ring.

The ester group remains unaffected.

Thus, product $$\mathrm{A}$$ contains a cyclic ketal at the original ketone position with the ester group unchanged.

Correct Option: $$\mathrm{B}$$